Gear-cutting machine



Nov. 26, 1929, H, D, COLMAN 1,737,217

GEAR CUTTING MACHINE original Filed April 24, 1925' mvENToR H Gummi. Emlnmn Patented Nov. Z6, 1929 HOWARD D. COLMAN, F ROCKFO'RD, ILLINOS,Y.ASSIGNOR T0 BARBER-COLMAR' COIT- l/ PANY, 0F ROCKFORD, ILLINGIS, ACGRPORATGN OF ILLINOS GEAR-CUTTING MACHINE l Application filed April24., 1925, Serial No. 25,496. Renewed April 17, 1929.

In application Serial No. 730,839 filed AugustI 8, 1924 (now Patent No.1,712,256, dated Mayy 7, 1929) l have disclosed a gearcutting machinecomprising a milling cutter of relatively large diameter having upon itsperiphery a plurality of annular series of cutter teeth of rack-toothform, the critter having at least as many peripheral series of cutterteeth as there are tooth spaces in the gear wheel to be cut. rlfhemachine also comprises means for rolling a gear vblank across theperiphery of the cutter, the latter in its rotation serving togenerategear teeth upon the blank. vInasmuch as the cutter teeth travel in thearc of a circle While in engagement with the gear blank, it will beevident that the sides of the teeth and the bottoms of the tooth spaceswill be somewhat concave, but in the machine shown in said applicationthe ratio of the thickness of the gear blank to the radius of the cutteris so great that the teeth generated approximate so closely to theproper form that but little stock remains to be removed in the finishingopera- '25 tion.

The object of the present invention is to improve the machine shown inthe abovementioned application so as to eliminate the ccncaving abovereferred to and to render practicable the use of a cutter of smaller d1-ameter and hence less costly.

In the accompanying drawings,

Figure 1 is a fragmental elevation of a gear-cutting machine embodyingthe features of my invention.

Fig. 2 is a fragmental sectional view of a gear wheel cut by means ofthe improved machine.

Fig. 3 is a View taken in the plane of line 3-3 of Fig. 1.

Fig. l is a diagrammatic view.

While the invention may` be applicable to cutters of other types,I haveherein shown a plurality of annular series of cutter teeth 2 (Fig. 3)said teeth being formed upon blades 6 (Fig. 1) secured within slots inthe body of the cutter. As shown in Fig. 1 the teeth 2 arecircumferentiallly spaced a distance cutter 1 provided upon itsperiphery with a` bearing openings 10 eccentrically formed in bushings11. The bushings 11 are mounted for oscillation in openings 12 providedin stationary bearing brackets 13 forming part of the machine framework.

rlhe cutter 1 is rotatedby Vmeans of a worm 14r- (Fig. 3) mounted upon ashaft 15 which is supported in bearings inthe machine frame, said wormmeshing with the f.

.worm wheel 8. y y p Y Means is provided for rolling a gear blank aacross the periphery of the cutter, which means may be like that fullydisclosed in the before-mentioned application Serial No. ,7d

7 30,839, or of any .preferred-construction. As theblank a mounted onthe arbor b is rolled past the cutter the latter generates gear teeth4.upon the peripheryfof the blank. In order toeliminate the concavinghereinbefore alluded to and make each gear tooth of uniformcross-section from end to end, l provide means vfor reciprocating thecutter 1l toward and away from thegear blank, the reciprocation being sotimedy and of such a characteras to `cause each cutter ltoothto'travelfin a path which is parallel to the axis of the blank duringthe time` the cutter tooth `is passing through the blank. The meansherein shown for thus reciprocating the cutter comprises two camsk 16fixed Aupon opposite ends of a lshaft 17 extending parallel with thecutter shaft 9 and rotatably mountedin suitable bearings in the machineframework. The shaft 17 is rotated by means of a bevel gear 18 (Fig. 3)fixed upon said shaft and mesh ing with a similar gear 19 which is fixedupon a shaft 20 mounted in bearings so as to extend parallel with theshaft 15. The shaft 2O is driven from the shaft 15 through intermeshinggears 21. Fixed to the Louter ends of the bushings 11 are arms 22carrying rollers 23 that bear upon the periphery ofthe cams 16. yReferring now to the diagram forming Fig. ,4: It will beapparent that asthey cams 16 revolve, the'arms 22 will bel swung up and down, thusoscillating the eccentric bushings 11 yso as to shift the shaft 9 bodilytoward and away from the gear blank a, the movement of translation ofthe shaft 9 being perpendicular to the axis of the gear blank, and thereciprocation being so timed that each cutter tooth travels in a:straight line while `passing through qthe blank. "Consequently #thegear teeth are given the same cross-sectional .form ,from end `v`to end.This isclearly-shovvn `in Fig. 2, Where thedotted ,line indicates thepath which the cutter teeth would take if the cutter l revolved upon astatiQDaryaXiS- The Worm Wheel 8 is, of course, reciprocatedWiththe-cutterl and .thus rolls back and forth along the Worm 14. Byreason of such-movement along the.worm,the cutter `1 when moved in onedirectionhas its rotation accelerated and When moved in the oppositedirection is retarded in its rotation. The cams 16 aresoshaped as tocompensate for such t alternate acceleration and retardation.

Inasmuchasthe cutter blades 6- are relatively expensive, itfis desirableto reduce the number-thereof as much as practicable. A substantialreduction over'that shown in application l.Serial `No.730,839 may beeffected-by reducing'the diameter ofthe cutter l as much as possibleWithout employing an excessive amplitude of oscillation.

It Will be understood that the construction 'herein'shoWn-maybe modifiedin various Ways without departing fromthe,spirit and scope of uthe'invention set forth Y. in `the `appended claims.

"I claim as my'invention: Y Y

1. A I`gear generatlngymachme having, 1n combination, a rotary cutter,meansfor supporting a blank in position to be cut'by the Vtimedrelationto each other, saidcam caus- `ing reciprocation ofV the cutter,perpendicuflarlyto the axis of thegblankf 3. A gearlgenerating machinehaving, in

combination, a rotary cutter, means tvfor supporting a blank in.position ,to-becut by the cutterfthe spacing of the cutter `teethibeingat least equal tothe thickness of lthe blank,

' and mechanismvfor rotating and reciprocatin l thefcutter, thereciprocation of ,the cutter bing-perpendicular-to the axis .of the"blank and so timed With relation to the peripheral speed of the cutterthat each cutter tooth travels in a path parallel to the axis of theblank While the tooth is passing through the blank.

4. A gear generating machine having, in combination, a rotaryfcutter,`-means Yfor supporting ablankin positiontmbe cutby the cutter, andmeans for causing relative re- .ciprocationbetvveen thecutter andtheblank perpendicularly .to 'the xaxis `of the -blank 'in such timedrelation'to the peripheral speed of .thecutter-that each cutter toothtravels in ference ofthe pitch circle ofthe gear orfblank 'toibeoperated upon, means for supporting a-gear-.or blank in position foraction thereon; by said Wheel, and Ymeans forfreclprocating AsaidWheelrelatively tothe gear orblankfto carry said active surfacesthrougha straight path While in engagement Withthe gear or lank. j l

yIn testimony whereof, I have hereunto ahxed'my signature.

